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Hepatitis B Vaccination Coverage Among Adults --- United States, 2004

Hepatitis B virus (HBV) infection is a major cause of cirrhosis and liver cancer in the United States.
The Advisory Committee on Immunization Practices (ACIP)
has recommended a comprehensive strategy to eliminate
HBV transmission, including prevention of perinatal HBV transmission; universal vaccination of infants; catch-up vaccination
of unvaccinated children and adolescents; and vaccination of unvaccinated adults at increased risk for infection. The
incidence of acute hepatitis B has declined 75%, from 8.5 per 100,000 population in 1990 to 2.1 per 100,000 population in 2004,
with the greatest declines (94%) among children and adolescents
(1). Incidence remains highest among adults, who accounted
for approximately 95% of the estimated 60,000 new infections in 2004. To measure hepatitis B vaccination coverage
among adults, data were analyzed from the 2004 National Health Interview Survey (NHIS). This report summarizes the results
of that analysis, which indicated that, during 2004, 34.6% of adults aged 18--49 years reported receiving hepatitis B
vaccine, including 45.4% of adults at high risk for HBV infection. To accelerate elimination of HBV transmission in the United
States, public health programs and clinical care providers should implement strategies to ensure that adults at high risk are
offered hepatitis B vaccine.

NHIS is a multipurpose household health survey of the U.S. civilian, noninstitutionalized population, conducted
by in-person interview. Hepatitis B vaccination coverage was
estimated from self reports of sampled adults. The analysis
was restricted to adults aged 18--49 years, age groups that
account for approximately 80% of adult HBV infections.

In the 2004 NHIS, adults who responded "yes" to the question, "Have you ever received hepatitis B vaccine?"
were assumed to have received >1 vaccine dose. For this analysis, adults were considered at high risk for HBV infection if
they reported a risk factor in answering any of three questions
related to human immunodeficiency virus (HIV) and
sexually transmitted disease (STD) risk behaviors.*

For all adults aged >18 years, weighted age-specific and
national hepatitis B vaccination coverage rates were
estimated. Statistical analysis software was used to calculate weighted estimates and confidence intervals. Chi-square tests were used
to compare coverage rates among groups. P-values <0.05 were considered statistically significant. Coverage rates with
relative standard errors >0.30 were not reported. A logistic model was developed to determine whether high risk was an
independent predictor of vaccination, including as possible confounders all terms identified to be predictors of vaccination in
univariate analysis and those that have been determined to be associated in other studies. The final model fit the data
(Hosmer-Lemeshow goodness-of-fit, p = 0.36).

During 2004, a total of 31,326 adults were interviewed, including 18,269 aged 18--49 years. The
response rate was 72.5% (2). Of eligible adults aged 18--49 years, 17,249 (94%) who responded to the hepatitis B vaccination questions were
included in this analysis, including 1,048 (5.7%) adults at high risk.

A weighted analysis of adults who were surveyed indicated that 34.6% (95% CI = 33.5%--35.6%)
reported receiving hepatitis B vaccine. Coverage was highest among persons aged 18--20 years and declined with increasing age (Table).
Coverage also was higher for persons in occupations for which vaccination is specifically recommended, including health-care
workers (80.5%; CI = 77.3%--83.4%) and police officers or firefighters (63.6%; CI = 56.6%--70.1%), and for adults at high
risk (45.4%; CI = 41.7%--49.2%).

Report of hepatitis B vaccination also was associated with certain population characteristics, including female sex,
non-Hispanic ethnicity, and higher educational achievement. Persons with a routine source of health care (e.g., primary
doctor, health maintenance organization, or
clinic)and persons with health insurance also were more likely to report vaccination
than those with no routine source of health care (Table). The same demographic and health-care use characteristics were
associated with higher likelihood of vaccination among persons at high risk as among other respondents. In a multivariate model,
after controlling for age, sex, education, occupation, and HIV test history, high risk remained a statistically significant
predictor (adjusted odds ratio = 1.3) of hepatitis B vaccination.

Editorial Note:

The findings in this report suggest that hepatitis B vaccination coverage among adults at high risk,
as measured by NHIS, has increased substantially from 30% in 2000 to 45% in 2004
(3). Some of this increase in coverage represents the aging of persons vaccinated as adolescents, reflecting the effect of ACIP recommendations for
routine vaccination of adolescents that were first made in 1995
(4). In addition, higher vaccination coverage among persons of all
ages at high risk suggests successes vaccinating targeted adults and likely contributed to a decline in hepatitis B incidence.
From 2000 to 2004, hepatitis B incidence among adults decreased 27%, from 3.7 to 2.7 per 100,000 population
(CDC, unpublished data, 2006). However, hepatitis B vaccination coverage of adults at high risk remained lower than
vaccination coverage of children (92%) and adolescents (86%) in 2004
(5), two other age groups included in the ACIP
vaccination strategy to eliminate HBV transmission.

Several factors contribute to low hepatitis B vaccination coverage among adults at high risk. In contrast to vaccination
of children, national programs that support vaccine purchase and infrastructure for vaccine administration are not available
for adults. As a result, adults at increased risk often have missed opportunities to receive hepatitis B vaccination. In a study of
483 adults with acute hepatitis B infection, 61% reported
a missed opportunity for vaccination during STD
treatment, incarceration, or drug treatment during 2001--2004
(6). In primary care settings, patients and providers might be reluctant
to discuss risk behaviors (7), and providers might not prioritize vaccination in the context of other clinical care services.

Adult vaccination coverage can be increased through the use of provider reminders and other interventions to increase
access to vaccination (8). Demonstration projects have determined that provision of comprehensive HIV, viral hepatitis, and
STD services increases vaccination coverage
(9). In October 2005, ACIP provisionally recommended strategies to
improve vaccination for adults at risk for hepatitis B,
emphasizing vaccination of all adults at venues where a high proportion
of persons are likely to have risk factors for HBV infection (e.g., STD/HIV testing and treatment facilities, correctional
facilities, and drug-abuse treatment facilities) and the adoption of practices that remove barriers to vaccination in primary care
settings (10).

The findings in this report are subject to at least four limitations. First, criteria for adults at high risk used in this
study might not identify all persons who are at risk for HBV infection, such as persons with multiple sex partners, and
might identify persons without risk, such as most persons with
hemophilia. Second, the in-person format of the interview might
lead to underreporting of risk behaviors. Third, hepatitis B vaccination was based on self-report and was not validated by
medical records. Although differences might exist between self-reported vaccination and true vaccination,
directional bias is unlikely, so correlates and trends in coverage are likely to reflect true trends. Finally, NHIS excludes all institutionalized persons
(e.g., military or incarcerated) among whom both the risk for hepatitis B and vaccination coverage might differ from those of
the rest of the population. Despite these limitations, NHIS is the only national survey that
collects data related to adult hepatitis B vaccination.

Hepatitis B vaccine is safe and effective and the only
licensed vaccine that prevents cancers. Despite these benefits,
the majority of adults at risk for HBV remain unvaccinated. To increase coverage, public health programs and primary
care providers should inform adults receiving preventive clinical services of the potential benefits of hepatitis B vaccination for
their
health, vaccinate all adults who seek protection from HBV, and adopt strategies appropriate for the practice setting to
ensure that all adults at risk for HBV infection are offered hepatitis B vaccine.

Acknowledgments

This report is based, in part, on data contributed by S Stokley, MPH, National Center for Immunization and Respiratory
Diseases (proposed); A Wasley, PhD, Div of Viral Hepatitis; and N Jain, MD, Div of STD Prevention, National Center for HIV, Viral
Hepatitis, STDs, and Tuberculosis Prevention
(proposed), CDC.

* 1) "What are your chances of getting HIV (the virus that causes AIDS)? Would you say high, medium, low, or none?"; 2) "In the past five years, have you had
an STD other than HIV or AIDS?"; 3) "Tell me if any of these statements is true for you; do not tell me which statement or statements are true for you; just if any
of them are: a) you have hemophilia and have received clotting factor concentrations; b) you are a man who has had sex with other men, even just one time; c)
you have taken street drugs by needle, even just one time; d) you have traded sex for money or drugs, even just one time; e) you have tested positive for HIV (the
virus that causes AIDS); f) you have had sex (even just one time) with someone who would answer `yes' to any of these statements."

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